Cameras for both day and night use have been developed for surveillance imaging. Additionally, the demand for lenses that operate in both the visible light region and the near infrared region for use both during the day and at night have been increasing. A great many zoom lenses have been designed for use in the visible light region. For example, a zoom lens for use in the visible light region is described in Japanese Laid-Open Patent Application 2001-194590. The lens described in this application is a four-group zoom lens with a zoom ratio of about ten to one.
However, conventional lenses that are designed for use only in the visible light region include chromatic aberrations in the images they produce that are large in the near infrared region. This causes the images to be not clearly focused when using the near infrared region for imaging at night. For this reason, a lens that favorably corrects aberrations in both the visible light region and the near infrared region is desired. In addition, particularly bright lens systems are desirable in surveillance cameras, especially for imaging at night. Furthermore, a zoom lens that can realize a ten to one zoom ratio in both the visible light region and in the near infrared region is desirable in order to comply with the various needs of the users.